Separation of petroleum ether extracted residue of low temperature coal tar by chromatography column and structural feature of fractions by TG-FTIR and PY-GC/MS

Abstract

The petroleum ether extracted residue (PCT) of the low temperature coal tar were separated and analyzed in this study. PCT was stepwise separated into toluene eluent (TS), ethanol eluent (EAS), methanol eluent (MAS), tetrahydrofuran eluent (THFS) and residue (IS) by chromatography column (CC) with Al2O3. Their composition and structure feature were confirmed by gel permeation chromatography (GPC), Uv-fluorescence, thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR), pyrolysis gas chromatography-mass spectrometer (PY-GC/MS) and Fourier transformed infrared (FTIR). The results show that the yields of TS, EAS, MAS, THFS are 1.70 wt%, 33.22 wt%, 18.97 wt% and 1.41 wt%, respectively. The order of their molecular weights from small to large is as follows: MAS < PCT < TS < EAS < THFS. The compound types of pyrolysis volatiles from TS, EAS, MAS and IS change completely with the temperature rising. TS pyrolysis volatiles mainly contain oxygen compounds and nitrogen compounds. EAS pyrolysis volatiles mainly contain aromatic hydrocarbons and oxygen compounds·THFS pyrolysis volatiles mainly contain aliphatic hydrocarbons (C33-C43 alkanes), and their average content is 82.39 wt%. The pyrolysis temperature from 500 °C to 600 °C is the cut-off point, at which light aromatic hydrocarbons and low boiling phenols are detected, and they may connected by bridge bonds.